Experimental Studies of Evolution in Guppies: A Model For Understanding the Evolutionary Consequences of Predator Removal in Natural Communities

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Experimental Studies of Evolution in Guppies: A Model For Understanding the Evolutionary Consequences of Predator Removal in Natural Communities David N.

1 Experimental Studies of Evolution in Guppies: A Model For Understanding the Evolutionary Consequences of Predator Removal in Natural Communities David N. Reznick University of California, Riverside UC Riverside Center for Conservation Biology Cameron K. Ghalambor Colorado State University Kevin R. Crooks Colorado State University

3 Apex predators are Susceptible to local extinction because - of selective targeting - low population density, low rates of reproduction Their loss can have manifold effects on the community (keystone effect)- e.g. proliferation of prey, loss of diversity

4 Starfish and Biodiversity in Inter-tidal Communities the Keystone Predator Concept (Paine 1974)

6 Such keystone effects are known from a diversity of environments Rainforests Temperate forests Old fields Open ocean Lakes

7 Other keystones, rewilding and the impact on naïve prey

8 What are the Evolutionary Consequences of Predator Removal then reintroduction? Ecological impacts of predator removal are well known. Little attention has been given to the evolutionary impacts Predator-prey dynamics (keystone effect) suggests strong co-evolutionary relationships

9 Today, we will Document rapid evolution of prey in response to removal of threat of predation Argue that such changes are sufficiently rapid and profound to require that they be accommodated in restoration efforts

10 Experimental studies of evolution in Trinidadian guppies. The best organisms for conservation studies may not be the endangered ones

12 Low Predation High Predation

14 Probability of Recapture (%) Probability of Recapture (%) (a) < >18 Size Class (mm) Low Predation High Predation Mark-recapture studies 12-day recapture interval Guppies suffer Significantly higher Mortality rates when Predators are present Mortality Rate Mortality Rate < >18 Size Class (mm)

15 Comparative Ecology In absence of predators, guppies: Are found at 4-5x higher densities Grow less rapidly Have lower birth and death rates Have a more even age-distribution (high predation populations are dominated by young, small fish)

16 Lab and Field Life History Results High vs. Low Predation Guppies from low predation environments have: - Delayed maturity - Reduced fecundity Both differences are predicted by life history theory. Both will reduce population growth rate.

17 1.6 Life Histories of Field Collected Females Embryo Weight (mg) Cren Eleo Riv Riv/Macro North Slope South Slope 9 8 Number of Offspring North Slope South Slope 3 2 Cren Eleo Riv Riv/Macro High Predation Low Predation

18 Other Evolutionary Consequences of Predator Removal in Guppy Populations 1. Male coloration (Endler 1980 ) 2. Shoaling response (Magurran et al. 1992) 3. Male and female fast start swimming (Ghalambor et al. 2004; Walker et al. 2005) 4. Survival probability in the presence of a natural predator (O Steen et al. 2002)

19 High Predation Low Predation

Rapid-start Performance Ghalambor et al. 2004, Am. Nat. Walker et at. 2005, Func. Ecol. Trait Predation Low High Body mass (mg) 447 (32) 491 (29) Max. acceleration (m/s/s) 53.3 (4.4) 67.4 (3.

20 Rapid-start Performance Ghalambor et al. 2004, Am. Nat. Walker et at. 2005, Func. Ecol. Trait Predation Low High Body mass (mg) 447 (32) 491 (29) Max. acceleration (m/s/s) 53.3 (4.4) 67.4 (3.7) Av. acceleration (m/s/s) 33.4 (3.2) 41.5 (2.6) Max. velocity (m/s).854 (.03).913 (.03) Av. velocity (m/s).594 (.02).615 (.01) 2 nd lab generation, two high and low predation localities Performance

22 Rates of Evolution After Experimental Reduction of Predation Risk Trait Time #Generations (Years) Male Coloration Male age and size at maturity Female age and size at maturity Offspring number and size Reproductive effort Predator Escape Schooling/predator inspection

23 Fate of guppies in response to predator reintroduction? Males are brightly colored Escape responses are less well developed Life histories are incompatible with high mortality rates (delayed maturity, lower fecundity)

24 Population Simulations in the Presence and Absence of Predators Number of Populations Surviving Low to Low Low to High Time

25 Policy Recommendatons 1. Exploit behavioral plasticity and prime prey species for predator reintroduction

26 Policy Recommendations 2. Integrate predator reintroduction with other aspects of habitat restoration

27 Policy Recommendatoins 3. Selection by human hunters is not a substitute for selection by natural predators Coltman et al. 2003, Nature 426

28 Policy Recommendatons 4. Some prey may not be able to survive rewilding Gene flow from prey populations that are adapted to predators

29 Responses to 5 Questions 1. Negative effects of rewilding : Introducing predators will likely cause an unexpected imbalancing of the ecosystem. It should be viewed as creating an episode of selection.

30 Responses, cont d 3. Recommended changes to conservation practices? See earlier recommendations - conditioning - monitoring of prey populations gene flow from adapted populations if necessary - integrated restoration

31 Responses, cont d 5. Future research? Foundations in Integrative Biological Research Program (FIBR - NSF): Experimental Studies of the Interface Between Ecological and Evolutionary Processes in a Natural Ecosystem David Reznick, Cameron Ghalambor, Andrew Hendry, Michael Kinnison Paul Bentzen, Doug Fraser, Jim Gilliam, Alex Flecker, Cathy Pringle, Steve Thomas, Regis Ferriere, Don Deangelis

32 Predators Within species (or within trophic level) Interactions (e.g. density dependence) Ecological effects Top-down forces Bottom-up forces Guppies Rivulus Genetic effects (selective pressure) Experimental manipulation Primary trophic level (algae and heterotrophic microbes) Nutrient availability and cycling Energy Flow Hydrology / Light

33 That s All Folks!

34 Susceptibility to Predation -2 nd Lab Generation O Steen et al, Evolution(2002) Comparison #Survivors(of 6) P-value High Pred. Low Pred Aripo River Aripo Intro (35 generations)

The Ecology of Organisms and Populations

CHAPTER 18 The Ecology of Organisms and Populations Figures 18.1 18.3 PowerPoint Lecture Slides for Essential Biology, Second Edition & Essential Biology with Physiology Presentation prepared by Chris